Multiple HC${}_3$N line observations towards 19 Galactic massive star-forming regions

Abstract

We performed observations of the HC${}_3$N (24-23, 17-16, 11-10, 8-7) lines towards a sample consisting of 19 Galactic massive star-forming regions with the Arizona Radio Observatory 12-m and Caltech Submillimeter Observatory 10.4-m telescopes. HC${}_3$N (24-23, 17-16, 11-10, 8-7) lines were detected in sources except for W44, where only HC${}_3$N (17-16, 11-10) were detected. Twelve of the nineteen sources showed probable line wing features. The excitation temperatures were estimated from the line ratio of HC${}_3$N (24-23) to HC${}_3$N (17-16) for 18 sources and are in the range 23-57 K. The line widths of higher-$J$ transitions are larger than lower-$J$ ones for most sources. This indicates that the inner dense warm regions have more violent turbulence or other motions (such as rotation) than outer regions in these sources. A possible cutoff tendency was found around $L_{\mathrm{IR}}$ $\sim$ 10${}^6$ $L_{\odot }$ in the relation between $L_{\mathrm{IR}}$ and full width at half maximum line widths.

arXiv commentAccepted for publication in PASJ

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